Most computers include a timekeeping module or system which keeps track of the present time of day and date using its own oscillator. These timekeeping systems receive their primary power from the computer system but have backup batteries in order to preserve the time data when the primary power source fails. Since the useful life of the backup battery depends generally on the amount current drawn by the timekeeping system, the power supply current used by the timekeeping system generally determines how often battery replacement is required. Therefore it can be appreciated that a timekeeping system which operates with a relatively small amount of power supply current is highly desirable.